I've got this to work again by renaming the Shores of Hazeron folder at C:\Users\YOURNAME\Shores of Hazeron and then letting the launcher download the files again. I bet the issue can be narrowed down to more specific files in the folder but this should work as a temporary fix.
EDIT: It's the "Temporary" folder in the Shores of Hazeron folder that seems to be the culprit. I've run into the bug again and then renamed that folder and that fixed it again.
EDIT: It's the "Temporary" folder in the Shores of Hazeron folder that seems to be the culprit. I've run into the bug again and then renamed that folder and that fixed it again.